Rain has been sweeping across Wales today, bringing a sodden end to what is likely to be one of the wettest years on record.

Some upland areas of South Wales saw nearly an inch of rain (20 to 25mm) in the six hours from 6am, said Julian Mayes, a senior forecaster with MeteoGroup, the weather division of the Press Association.

“That’s going to be making rivers rise temporarily at least, and causing more concern,” he said.

There was heavy rain overnight in many areas – Capel Curig in Snowdonia 48mm in the 12 hours between 6pm yesterday and 6am today.

That has led to disruption to rail services, with Arriva Trains Wales warning passengers that all lines between North Llanriwst and Blaenau Ffestiniog are closed.

The company said: “Train services running through these stations may be terminated at and started back from North Llanrwst at short notice. An estimate for the resumption of normal services will be provided as soon as the problem has been fully assessed.”

A replacement bus service has been put in place for the route.

The A4042 in Abergavenny has been closed in both directions between the Hardwick roundabout and Little Mill because of flooding.

Traffic Wales said the road was closed at around 1pm today and is expected to be closed until 5pm.

“It was one of those nights when the rain gets a lot heavier over the hills, partly because it was windy,” Mr Mayes said.

The Environment Agency has 211 flood alerts and 90 flood warnings in place in areas where the ground is already saturated and rivers and groundwater levels are still high.

They follow hundreds of other alerts issued this month, as several days’ worth of rain fell in a few hours at its worst, contributing to a year of bad weather which has left the UK on the brink of its wettest since records began in 1910.

The start of 2013 is expected to bring some much desired respite from the rain.

“This latest band is moving south east, and should clear London by about 9pm, giving hope that it may be dry for the New Year celebrations, though turning colder,” Mr Mayes said.

Flood warnings from Environment Agency Wales are in place for the Lower Dee Valley, the Conwy Valley, the Dyfi Valley and Tenby’s River Ritec.

There are also flood alerts across the nation, including South Pembrokeshire and Swansea Bay and much of South Wales – including the River Taff from Merthyr to Cardiff.

Graham Hillier, from Environment Agency Wales, said: “We’re asking people to take extra care as the risk of flooding continues.”

Firefighters in Mid and West Wales were called to flooding incidents on Saturday at Milford Haven, Aberporth and Caldey Island, off Tenby in Pembrokeshire.

Crews were forced to travel by lifeboat to the monks on Caldey Island after heavy rain left a holiday home owned by the abbey under two feet of water.

Emergency services also received calls after two canoeists capsized in the fast-flowing River Towy, near Llandovery, and a dog fell off a swollen waterfall at Ystradfellte in the Brecon Beacons.

According to the Met Office, just 1.8in (46mm) of rain is needed to fall before midnight tonight to make this year the wettest across the UK since records began in 1910.

A new high for England has already been set with 43.1in (1,095.8mm) falling between January 1 and Boxing Day.

The Welsh record has not yet been broken and a Met Office spokesman said they would calculate in the coming days if the record had been matched.